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Biomedical subjects

B Jégou

Publications and source records attributed to B Jégou.

At least 19 recordsLinked to original sources
PubMed2007

Transferrin overexpression alters testicular function in aged mice.

Many studies have shown a correlation between transferrin (Tf) concentration and sperm yield in several mammalian species. We have used transgenic mice expressing human Tf (hTf) to investigate if overexpression of Tf increases the efficiency of mouse spermatogenesis. We demonstrated that a 36% increase of Tf does not ameliorate the efficiency of mouse spermatogenesis but on the contrary resulted in a 36% decrease of testis sperm reserves. Tf overexpression had no effect on testicular determination and development, however testicular function of these transgenic mice was affected in an age-dependent manner. At 16 months of age, testicular and epididymal weights were significantly reduced. While spermatogenesis was qualitatively normal, testicular functions were perturbed. In fact, testosterone rate after human chorionic gonadotropin (hCG) stimulation was lower in Tf overexpressing mice. Intratesticular concentration of estradiol-17beta was increased and fluid accumulation after ligation of rete testis was more abundant in these transgenic mice. Surprisingly, we found that endogenous Tf levels were also increased in Tf overexpressing mice and we demonstrated for the first time that Tf may serve to upregulate its own expression in testis. Collectively, our data show that Tf overexpression has negative effects on testicular function and that Tf levels require strict regulation in the testis.

Animals↗
PubMed2006

Human testis in organotypic culture: application for basic or clinical research.

BACKGROUND: Over recent decades, recurring efforts have been devoted to developing testicular cell or tissue cultures for basic and clinical research. However, there remains much confusion, particularly concerning the fate of human germ cells in culture. OBJECTIVE: To reassess the status of human testicular cell types as well as the ability of germ cells to divide and differentiate in organotypic culture. METHODS: Human testicular fragments were maintained for 2 weeks in culture. The viability and functionality of testicular cells were assessed using light and electronic microscopy, apoptotic cell labelling, 5-bromo-2'-deoxyuridine (BrdU) incorporation, immunohistochemistry and quantitative PCR against specific cell markers. RESULTS: A gradual loss of meiotic and post-meiotic germ cells occurred throughout the culture period, irrespective of the presence of gonadotrophins. However, all germ cell types remained traceable for up to 16 days, some still dividing and differentiating at a rate compatible with the in vivo situation. Good maintenance of the general architecture of the explants associated with clearly quantifiable levels of several somatic cell markers was observed. CONCLUSION: Although this culture model is clearly unsuitable for preparing germ cells for therapeutic purposes, it does represent a most valuable tool for testing the effects of biological and chemical agents on testicular tissue.

Bromodeoxyuridine↗
PubMed2006

[Breakthroughs in the study of the influence of environmental factors on male reproductive health].

BACKGROUND: An important part of the research effort on male reproductive health focus on two important questions: on the one side, that of the temporal deterioration of male reproductive health and, on the other head, that of the influence of exposure to environmental chemicals during intra-uterine life on health during childhood and adulthood. The concepts on endocrine disruption and testicular dysgenesis syndrome make a link between these two questions. METHODS: This work examines knowledge cumulated over the last couple of years concerning geographical and temporal variations in male reproductive health and the testicular dysgenesis syndrome. Recent results concerning the concept of endocrine disruption and on the environmental influences on male reproduction are presented, as well as on the transgenerational effects on environmental factors on the health of male children. CONCLUSIONS: Based on clinical and epidemiological data, and with the use of in vitro animal models as well as observations in wildlife, research in this field has enabled progress in the elucidation of mechanisms of action and characterization of environmental influences on male reproductive health.

Environmental Exposure↗
PubMed2004

Expression, regulation, and immunolocalization of putative homeodomain transcription factor 1 (PHTF1) in rodent epididymis: evidence for a novel form resulting from proteolytic cleavage.

PHTF1 is an 84-86-kDa membrane protein found in the endoplasmic reticulum of male germ cells in rodents. There are no evident signs of PHTF1 in the spermatozoa released into the lumen of the seminiferous tubules but PHTF1 is present in the epididymal epithelium. Characterization of the epididymal Phtf1 messenger by Northern blot and reverse transcription-PCR identified a 3-kilobase transcript in the epididymis, similar to that previously reported in the testis. The transcript is present in the proximal part of the epididymis and it appears when the rats reach 4 wk of age. Through immunofluorescence analysis, PHTF1 was localized in the principal cells of the initial segment and the caput epididymis. Colocalization with different markers indicated PHTF1 is in the endoplasmic reticulum saccules applied to the trans face of the Golgi system. Western blot analyses revealed a shorter form of the protein--about 56-kDa versus the 84-kDa form found in the testis. Using the canine epididymal cell line CIM 20, transfected by N- and C-terminal myc-tagged PHTF1, we demonstrated that the 56-kDa epididymal form could result from proteolytical processing.

Animals↗
PubMed2004

GermOnline, a cross-species community knowledgebase on germ cell differentiation.

GermOnline provides information and microarray expression data for genes involved in mitosis and meiosis, gamete formation and germ line development across species. The database has been developed, and is being curated and updated, by life scientists in cooperation with bioinformaticists. Information is contributed through an online form using free text, images and the controlled vocabulary developed by the GeneOntology Consortium. Authors provide up to three references in support of their contribution. The database is governed by an international board of scientists to ensure a standardized data format and the highest quality of GermOnline's information content. Release 2.0 provides exclusive access to microarray expression data from Saccharomyces cerevisiae and Rattus norvegicus, as well as curated information on approximately 700 genes from various organisms. The locus report pages include links to external databases that contain relevant annotation, microarray expression and proteome data. Conversely, the Saccharomyces Genome Database (SGD), S.cerevisiae GeneDB and Swiss-Prot link to the budding yeast section of GermOnline from their respective locus pages. GermOnline, a fully operational prototype subject-oriented knowledgebase designed for community annotation and array data visualization, is accessible at http://www.germonline.org. The target audience includes researchers who work on mitotic cell division, meiosis, gametogenesis, germ line development, human reproductive health and comparative genomics.

Animals↗
PubMed2004

Viruses in semen and male genital tissues--consequences for the reproductive system and therapeutic perspectives.

Sexually transmissible diseases such as AIDS have renewed the attention paid to viruses capable of infecting the male genital tract. The presence of viruses at this level may not only lead to their transmission and spread via semen but may also impact on male fertility and/or represent a potential cause of genital organ cancers. This review summarizes the currently available data on the various viruses identified in the human semen and male reproductive tract, their distribution in tissues and fluids, their possible cell targets and the functional consequences of their infectivity on the reproductive and endocrine systems. The use of medically assisted reproduction as a therapeutic tool in serodiscordant couples, as well as treatment strategies that need to be developed in order to eradicate these viruses from the male genital tract, are discussed.

Animals↗
PubMed2003

Experimental inoculation of the adult rat testis with Sendai virus: effect on testicular morphology and leukocyte population.

BACKGROUND: Surprisingly little is known about the interactions between viruses and the male uro-genital tract. These are important, as viral testicular orchitis, induced by mumps or human immunodeficiency virus (HIV) infection for example, can lead to sterility. Moreover, semen is an essential vector in the propagation of sexually transmissible viral diseases. Here, we studied the effects of testicular infection with Sendai virus, a virus related to mumps virus, on the cellular distribution of viral particles and on testicular morphology, with particular attention to the testicular leukocyte population. METHODS: At 5, 9, 11 or 24 h post-injection of Sendai virus through the scrotum, the testes were fixed for morphological and immunohistological studies. Localization of virus particles and numeration of leukocytes were performed using specific antibodies and morphological criteria. RESULTS: As early as 5 h post-injection, a rapid and massive infiltration of leukocytes was observed in the interstitial tissue. The peritubular cell layer and the most external part of the basal portion of the seminiferous tubules were altered. The virus was diffusely located within the interstitial tissue 9 h following the injection whereas, after 24 h, viral proteins were restricted to the cytoplasm of infiltrated leukocytes. The number of leukocytes increased with time post-injection. Thus, 24 h post-injection, CD3+ T-cell number was 3-fold higher, ED1+ monocyte number was 4-fold higher and polynuclear cell number was 600-fold higher than in the control testes (P<0.001 all observations). In contrast, the population of resident macrophages was unaffected by Sendai virus. CONCLUSIONS: Testicular viral infection causes inflammation including rapid recruitment of leukocytes. The experiments presented here provide a model for further studies on the etiopathology of viral orchitis, in particular that caused by mumps virus.

Animals↗
PubMed2003

Phtf1 is an integral membrane protein localized in an endoplasmic reticulum domain in maturing male germ cells.

Phtf1 is a gene evolutionarily conserved from Drosophila to human that is abundantly expressed in testis. In adult rat, transcripts were abundant in germinal meiotic and postmeiotic cells. Phtf1-specific antibodies revealed weak activity in a juxtanuclear region of early pachytene spermatocytes. Labeling progressively extended to the entire cytoplasm of step 2-3 spermatids, became intense from step 4, and persisted until the end of spermiogenesis, when it was eliminated in the residual bodies. Phtf1 displayed the properties of an integral membrane protein. In transfected cells and haploid cells of rat seminiferous epithelium, it colocalized with ER markers (calnexin and calmegin, respectively). By using both ER and Golgi markers (TGN-38, p58), we were able to show that, in pachytene spermatocytes and in Golgi phase spermatids, phtf1 labeled a region neighboring the cis-Golgi that probably corresponded to the peripheral Golgi region. Phtf1 staining was not related to beta-COP, AP1, or AP2 aptamers, indicating that it was not transported between Golgi saccules or between the Golgi complex and plasma membrane. However, aptamer labeling showed that chlatrin vesicles could be engaged in a new traffic route, raising the possibility of a meiotic proacrosomal vesicle origin. Colocalization between phtf1 and calmegin decreased during the acrosomal phase. During the maturation phase, phtf1 was able to identify different ER domains, as described previously for the peripheral Golgi region. Phtf1 provides a potential new marker for Golgi modifications as well as for many of the obscure transformations undergone by the endoplasmic reticulum. It could help to elucidate the morphogenic events connected with the transformation of spermatogenic cells.

3T3 Cells↗
PubMed2001

MAGE-A4, a germ cell specific marker, is expressed differentially in testicular tumors.

BACKGROUND: Testicular germ cell tumors are the most common malignancy in young males, and the frequency of these tumors has risen dramatically over the last century. Because it is known that the MAGE genes are expressed in a wide variety of tumors but are expressed only in the mitotic spermatogonia (germ cells) and in the primary spermatocytes in the normal testis, the authors screened the expression of MAGE-A4 in a panel of testicular germ cell tumors. METHODS: Monoclonal antibody 57B raised against MAGE-A4 was tested immunohistochemically on 12 classical seminomas, 5 anaplastic seminomas, 10 various specimens of nonseminomatous germ cell tumors (NSGCTs), 2 combined tumors containing seminoma components, 1 Sertoli cell tumor, 2 Leydig cell tumors, and 15 carcinomas in situ (CIS). In addition, monoclonal antibody 57B was tested on embryonic gonad (age 8 weeks) and fetal gonads (ages 15 weeks, 17 weeks, and 28 weeks). RESULTS: Classical seminomas uniformly and specifically expressed MAGE-A4 compared with anaplastic seminomas and NSGCTs, which were negative for this antigen. Specific expression of MAGE-A4 also was seen in subpopulations of CIS cells, providing additional evidence for heterogeneity of the phenotype of these cells, in which it is believed that differentiation and proliferation generate seminomas and NSGCTs. Finally, MAGE-A4 was expressed in the fetal precursors of the stem germ cells from 17 weeks of gestation onward, in accordance the fact that CIS can arise from prespermatogonia in the fetus. CONCLUSIONS: MAGE-A4 can be considered a potential specific marker for normal premeiotic germ cells and germ cell tumors and can be used to characterize classical seminomas.

Antigens, Neoplasm↗
PubMed2001

Cellular distribution of translationally controlled tumor protein in rat and human testes.

In a recent proteomic study we identified 53 spermatogonial proteins among which was the translationally controlled tumor protein (TCTP). This is a protein previously reported as being implicated in proliferation events in normal and tumoral tissues that had never previously been seen in the testis. The present study was aimed at establishing the complete cellular distribution of TCTP and its transcript and the ontogenetic expression of this gene within the testis. Using an immunohistochemistry technique, an intense TCTP signal was detected in gonocytes (the prespermatogonia) in the fetal rat testis and in spermatogonia within adult human and neonatal and adult rat testes. Meiotic spermatocytes and postmeiotic haploid spermatids were also strongly immunostained in a stage-dependent manner in human and rat testes. In addition, different levels of TCTP expression were also observed in the testicular somatic cells, with strong expression in Leydig cells and peritubular cells, and weak expression in Sertoli cells. Western and Northern blot analyses confirmed the presence of TCTP at all ages studied, with higher levels of RNA expression at 9 and 20 d postpartum, when spermatogonia and primary spermatocytes represent the highest proportion of germ cells: it was also confirmed that TCTP is present in all populations of isolated testicular cells. A transcript of 0.85 kb corresponding to TCTP, was expressed at all ages studied. This transcript was found to be expressed strongly in spermatogonia, somewhat less in isolated Leydig, resident macrophage, peritubular and Sertoli cells, weakly in the primary spermatocytes but not at all in spermatids. Interestingly, in the latter, a different transcript of 1.1 kb was present. The same 1.1 kb transcript appeared in testis extracts from 35 days postpartum onwards, corresponding to an age when spermatids accumulate within the tubules. Of note is that resident macrophages were found to express both the 0.85 and the 1.1 kb transcripts. We conclude that the strong expression of TCTP in spermatogonia makes it highly likely that the protein plays a significant role in spermatogenesis.

Adult↗
PubMed2001

Proteome analysis of rat spermatogonia: reinvestigation of stathmin spatio-temporal expression within the testis.

Stathmin is a protein known to be involved in various cell processes including cell proliferation and differentiation. It has already been described in the testis but its recent identification using a proteomic approach in mitotic spermatogenetic stem cells named spermatogonia (Guillaume et al., 2000) has lead us to reinvestigate its expression within the testis. Stathmin and its mRNAs were studied in isolated cells by Western and Northern blots and in situ using immunohistochemistry. We demonstrated that stathmin is indeed expressed in spermatogonia, and that it is also intensively expressed in the meiotic spermatocytes and in the first generations of spermatids. Furthermore, we showed aggregations of the protein in the cytoplasm of the later generations of spermatids preceding its elimination at the time of spermiation. Our Northern blots reveal the presence of two stathmin transcripts of 1.1 and 3.2 kb within the testis from the fetal stage onwards, in spermatogonia, spermatocytes, and spermatids. However, the 3.2 kb RNA transcript was barely detectable in the spermatids. Stathmin expression is known to be associated with microtubule dynamics. Therefore, its expression in the germ line is most probably related to the extremely complex structural cellular rearrangements occurring in germ cells during spermatogenesis. However, the exact role of stathmin and the reason of the existence of two transcripts in the male germ lineage awaits further investigation.

Animals↗
PubMed2001

Viruses in the mammalian male genital tract and their effects on the reproductive system.

This review describes the various viruses identified in the semen and reproductive tracts of mammals (including humans), their distribution in tissues and fluids, their possible cell targets, and the functional consequences of their infectivity on the reproductive and endocrine systems. The consequences of these viral infections on the reproductive tract and semen can be extremely serious in terms of organ integrity, development of pathological and cancerous processes, and transmission of diseases. Furthermore, of essential importance is the fact that viral infection of the testicular cells may result not only in changes in testicular function, a serious risk for the fertility and general health of the individual (such as a fall in testosteronemia leading to cachexia), but also in the possible transmission of virus-induced mutations to subsequent generations. In addition to providing an exhaustive account of the data available in these domains, this review focuses attention on the fact that the interface between endocrinology and virology has so far been poorly explored, particularly when major health, social and economical problems are posed. Our conclusions highlight the research strategies that need to be developed. Progress in all these domains is essential for the development of new treatment strategies to eradicate viruses and to correct the virus-induced dysfunction of the endocrine system.

Adenoviridae↗
PubMed2000

Testis hormone-sensitive lipase expression in spermatids is governed by a short promoter in transgenic mice.

A testicular form of hormone-sensitive lipase (HSL(tes)), a triacylglycerol lipase, and cholesterol esterase, is expressed in male germ cells. Northern blot analysis showed HSL(tes) mRNA expression in early spermatids. Immunolocalization of the protein in human and rodent seminiferous tubules indicated that the highest level of expression occurred in elongated spermatids. We have previously shown that 0.5 kilobase pairs of the human HSL(tes) promoter directs testis-specific expression of a chloramphenicol acetyltransferase reporter gene in transgenic mice and determined regions binding nuclear proteins expressed in testis but not in liver (Blaise, R., Grober, J., Rouet, P., Tavernier, G., Daegelen, D., and Langin, D. (1999) J. Biol. Chem. 274, 9327-9334). Mutation of a SRY/Sox-binding site in one of the regions did not impair in vivo testis-specific expression of the reporter gene. Further transgenic analyses established that 95 base pairs upstream of the transcription start site were sufficient for correct testis expression. In gel retardation assays using early spermatid nuclear extracts, a germ cell-specific DNA-protein interaction was mapped between -46 and -29 base pairs. The DNA binding nuclear protein showed properties of zinc finger transcription factors. Mutation of the region abolished reporter gene activity in transgenic mice, showing that it is necessary for testis expression of HSL(tes).

Animals↗
PubMed2000

Involvement of Bcl-2 family proteins in germ cell apoptosis during testicular development in the rat and pro-survival effect of stem cell factor on germ cells in vitro.

A large part of germ cells die apoptotically during testicular development in rodents. In the present study, a wave of germ cell apoptosis was observed between days 10 and 30 of postnatal life by in situ 3'-end labeling and DNA fragmentation analysis. To explore the potential involvement of Bcl-2 family members in this process, the expression and localization of some Bcl-2 family proteins (Bcl-2, Bcl-xL, Bcl-w, Bak, Bax, and Bad) and p53 were analyzed during testicular development in the rat by Western blotting and immunohistochemistry. The dynamic changes in the expression profiles of Bcl-2 family proteins are consistent with a model in which germ cells are primed for apoptosis during the first cycle of spermatogenesis by de novo expression of the death effectors Bax and Bad in a p53-dependent manner and these proteins are prevented from triggering further apoptosis after the first spermatogenic cycle has been set up by anti-apoptotic Bcl-2 family proteins Bcl-xL and Bcl-w. To examine whether the pro-survival effect of stem cell factor (SCF) on germ cells in vitro is mediated by Bcl-2 family proteins, the correlation between the pro-survival effect of SCF on germ cells and the expression of the above-mentioned apoptosis-related gene products in the seminiferous tubules at stage XII of the epithelial cycle were also investigated using a tubular culture system. The data suggest that SCF supports germ cell survival during spermatogenesis by up-regulating pro-survival Bcl-2 family proteins, Bcl-w and Bcl-xL, and down-regulating pro-apoptosis Bcl-2 family proteins, e.g. Bax.

Animals↗